Apparatus for bending tubing



Sept. 1 1953 Filed June 21, 1952 H. 0. JENNINGS, JR 2,650,636

APPARATUS FOR BENDING TUBING 2 Sheets-Sheet 1 llllllglillllllllwlllllllqlllw HQQEV c: JfA/N/A/GZS, ue

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Sept. 1, 1953- H. c. JENNINGS, JR

APPARATUS FOR BENDINQ TUBING 2 Sheets-Sheet 2 Filed June 21, 1952INVENTOR.

w 5 W N f a y E W H Mam Patented Sept. 1, 1953 UNITED STATfiS PATENTOFFICE APPARATUS FOR BENDING TUBING Harry G. Jennings, J12, Los Angeles,Calif.

Application June 21, 1952, Serial No. 294,787

1 Claim. 1

This invention relates to an apparatus for bending tubing.

In the construction of wheel chairs, certain types of porch furniture,and similar articles, the frame is formed of sections of seamless metaltubing. This tubing is frequently bent to provide elements of the frame.For example, a leg of a wheel chair may have its upper end bent atapproximately right angles thereto to provide an armrest. There are anumber of other situations where it is desirable or necessary to bendthe tubing at various angles, frequently at right angles.

When ordinary cylindrical tubing, such as is used in wheel chairs, porchfurniture and the like, is bent severely the outer side of the tubing isstretched and the inner side of the tubing is greatly compressed eventhough the tubing is bent around the end of a mandrel that is insertedtherein. The compression on the inner side of the tubing is such as toproduce a plurality of transversely extending wrinkles or corrugations.These corrugation-s produce a roughened surface on the inner side of thebend: which is objectionable for a number of reasons including that ofunsightliness.

An object of the present invention is to provide an apparatus forbending tubing wherein the wall of the tubing at'the inner side of thebend is longitudinally indented in the course of the bending operation.By indenting the tubing Wall in this manner the objectionable transversecorrugations are avoided and in lieu thereof a relatively short narrowlongitudinal indentation is formed at the inner side of the bend whichis normally in a position so that it is concealed or not readilyobservable.

With the foregoing and other objects in view, which will be mademanifest in the followin detailed description and specifically pointedout in the appended claim, reference is had to the accompanying drawingsfor an illustrative embodiment of the invention, wherein:

Figure l. is a top plan view of a portion of a bending apparatusembodying the present invention, parts being broken away and shown inhorizontal section and illustrating a section of tubing as having beenmounted thereon preparatory to being bent;

Fig. 2 is a view similar to Fig. 1 but illustrating the bend as havingbeen completed;

Fig. 3 is a horizontal section taken substantially upon the line 33 uponFig. 2;

Fig. 4 is a view similar to Fig. 2 but illustrating the tubing as beingin the process of being bent;

Fig. 5 is a horizontal section taken substantially upon the line 55 uponFig. 4 in the direction indicated; and

Fig. 6 is a perspective view of a portion of bent tubing which has beenbent in accordance with the present invention.

Referring to the accompanying drawings wherein similar referencecharacters designate similar parts throughout, the major portion of thebending apparatus disclosed conforms to one form of tubing bendingapparatus that is now in genera1 use. Consequently all details thereofhave not been illustrated. Essentially the apparatus disclosed consistsof a mandrel Iii on which a section of seamless metal tubing T isadapted to be telescoped. This mandrel is usually mounted on a limberrod. arranged axiallyoi its end which holds the mandrel againstlongitudinal or axial displacement but enables lateral movement to someextent.

On one side of the mandrel there is swingably mounted a jaw H which issemi-cylindrically recessed, as at 12, to accommodate approximatelyone-half of the cylindrical tubing. This jaw is swingably mounted forswinging movement about a pivot provided by a vertical shaft I3. Thispivot may be forcibly rotated either by power or manually. Attached tothe jaw H is a semicircular roll it which has a groove l5 extendingaround its semi-circular periphery and centrally of this groove there isan outwardly projecting rib It. The end of the mandrel is rounded off,as indicated at H, and that portion of the mandrel which is adjacent itsend and which is opposite the rib H5 is longitudinally grooved asindicated at IS. A movable jaw 19 is mounted on the jaw l l and isadapted to be tightened toward the jaw H by means of a manually operatedeccentric 20 so that that portion of the tubing which projects beyondthe end of the mandrel I0 may be clamped between the two jaws I9 and I land swung thereby about the pivot It. In so doing the tubing is axiallyshifted and bent, the bendin action taking place about the roundedoffend ll which is concentrically arranged with respect to the pivot It. Onthe opposite side of the mandrel Hi from the roll It there is a movablesupport El adapted to be advanced and retracted by means of a manuallyoperated linkage 22. This support has rollers 23 and slidably supportsagainst the rollers a follow block 2 1. The follow block 26 is groovedto accommodate approximately one-half of the tubing T. When it isdesired to bend the tubing the tubing is telescoped onto the mandrel andthe jaw 19 tightened toward the jaw II. The support 2| is also advancedso that it crowds the tubin and the mandrel toward the roll I4. The jawI I, movable jaw l8 and roll 14 are then swung as a unitary structureabout the axis of the vertical shaft [3, thus bending the tubing aroundthe rounded end I! of the mandrel. As this bending takes place thefollow block 24 rolls against the rollers '23 and moves with the tubingfrom the position shown in Fig. 1, through the position shown in Fig. 4,to the position shown in Fig. 2. As the bending takes place the rib I6indents or depresses the tubing wall at the inside of the bend into thegroove [8 thu producing on the inside of the bend a short narrowindentation indicated at 25 on Fig. 6. As will be noted from aninspection of the drawing, if the roll employed is to bend the tubingthrough a ninety degree bend, the rib l6 occupies an arc of less thanninety degrees of the roll. The ends of the rib are beveled 01f, asindicated at 26 and 27, to be tangent to the bottom or back of thegroove I 5. These beveled portions on the rib enable the tubing to beslipped onto the mandrel, in Fig. 1, without interfering with the riband after the bending is complete the bevel at 21 is disposed oppositethe mandrel, enabling the tubing to be slid off of the mandrel when thebend is completed. In other words, in both extreme positions the rib I6is disposed wholly outside of the groove 18. But in the intermediateposition, shown in Fig. 4, the rib I6 enters the groove I8 producing thedepression at 25. This depression extends only along the inside of thebend in the tubing and usually it will be located on the under side of astructural element of a wheel chair, porch furniture or the like.Consequently it is not readily observed. The indenting of the tubingwall at this point enables the bend to be made Without the formation oftransverse creases or corrugations such as are formed when the tubing isbent without employing the rib 16 or the groove l8. Consequently in sideelevation tubing bent in this manner appears to have a smooth continuousbend.

The conventional tube bending apparatus may be readily modified to adaptthe present invention by merely grooving the end of the mandrel with agroove l8 and providing a semicircular roll M on which a rib I6 isformed. Usually in the construction of these rolls two half rolls areheld in assembled relation and are turned on a lathe so as to form thegroove and a continuous rib l6. Thereafter the bevels at 26 and 21 maybe formed by grinding off the ends of the rib so that these bevels willbe disposed opposite the mandrel at both extreme positions of the roll.

From the above described construction it will be appreciated that anovel method and apparatus is provided for bending tubing wherein by theformation of a narrow longitudinal indentation in the tubing wall at theinside of the bend a smooth bend can be secured, avoiding the formationof transverse corrugations.

Various changes may be made in the details of the construction withoutdeparting from the spirit and scope of the invention as defined by theappended claim.

I claim:

A tube bending apparatus comprising a man drel on which tubing to bebent may be telescoped, a roll rotatably mounted adjacent the end of themandrel, the end of the mandrel being rounded off with a radius ofcurvature approximately concentric'with the axis of rotation of theroll, means for clamping the tubing against the roll, means for swingingthe clamping means and roll about the axis of rotation of the roll, afollow block mounted for movement longitudinally of the mandrel on theopposite side thereof from the roll, there being a circumferentiallyextending rib extending partially around the roll, the ends of the ribbeing beveled off approximately tangent to the roll, and there being agroove formed in the mandrel opposite the roll and extending to therounded end of the mandrel whereby as the roll and clamping means areswung the rib will depress the tubing into the groove over a portion ofthe interior of the bend in the tubing and the tubing may thereafter beremoved from the mandrel by sliding it longitudinally off of the end ofthe mandrel.

HARRY C. JENNINGS, JR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,285,275 Harder June 2, 1942 2,357,873 Bower Sept. 12, 1944FOREIGN PATENTS Number Country Date 271,815 Great Britain July 21, 1927

